Does your skin get really itchy when you run, bike, or lift weights? If it does, you could suffer from a physical allergy that causes you to itch when you exercise. Greatest allergy ever? Sure, maybe – unless you've got the version that makes it miserable to even climb stairs.

As Roberta Kwok explains in a recent post at Last Word on Nothing, the condition is called "cholinergic urticaria." According to Kwok – who thinks she may suffer from the allergy, herself – the symptoms, while rare, can be downright excruciating:

A quick Google search brought up complaints from dozens of fellowsufferers, who described the sensation as “an INSANE itch,” “pure hell,” and enough to make them want to “scratch until I bleed,” “take a knife to my legs,” or — my favourite — “blast my face off.”

Some people have found relief by taking antihistamines before they run. One 25-year-old patient, however, had a case so severe that he began to itch even when climbing a flight of stairs or carrying groceries. Antihistamines didn’t help him, but antibodies against immunoglobulin E, a protein involved in allergic reactions, did.